Uncompromised Landscape Lens for A7R?

Since we have bought, or will buy the A7R because it is light, full frame and has a great sensor, is there a landscape lens(24mm or less) that doesn't undermine those essential attributes?

That eliminates hefty SLR lenses on adaptors, legacy lenses that require cropping and/or software solutions for colour issues and vignetting, and mediocre optics that compromise the IQ and resolution potential of the A7R sensor.

Any first hand experience with an excellent lightweight landscape lens that brings the best out of this camera?